High-Performance Ag-Doped Na<sub>0.67</sub>MnO<sub>2</sub> Cathode: Operando XRD Study and Full-Cell Performance Analysis with Presodiated Anode
Burcu Kalyoncuoğlu, Metin Özgül, Sebahat Altundağ, Emine Altin, Iqra Moeez, Kyung Yoon Chung, Muhammad Arshad, Mustafa Göktan Aydın, Tolga Depçi, Serdar Altın, Sevda Sahinbay
Abstract
The key challenges of Na-ion batteries are to design structurally stable electrodes and reach high-enough capacities with full-cells. In this study, we report the positive effects of Ag substitution/addition to Na 0.67 MnO 2 . We determined that some of the intended Ag was incorporated into the structure, while the rest remained in metallic form. Ag substitution/addition increases the capacity (208 mA h/g at C/3 rate) and improves the cycle life of Na 0.67 MnO 2 (42% capacity fade with 100 cycles) in half-cells. We attribute these results to an enlarged interlayer spacing due to the large ionic radius of Ag, a suppressed Jahn–Teller effect due to the reduced number of Mn 3+ ions, and an increased electrical conductivity due to the presence of metallic Ag. We also produced full-cells with an electrochemically presodiated hard carbon anode. We reached a very high initial capacity of 190 mA h/g at the C/3 rate, showing that Ag substituted/added Na 0.67 MnO 2 is a promising candidate for commercialization of Na-ion batteries.